/* * hugepage-mmap: * * Example of using huge page memory in a user application using the mmap * system call. Before running this application, make sure that the * administrator has mounted the hugetlbfs filesystem (on some directory * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this * example, the app is requesting memory of size 256MB that is backed by * huge pages. * * For the ia64 architecture, the Linux kernel reserves Region number 4 for * huge pages. That means that if one requires a fixed address, a huge page * aligned address starting with 0x800000... will be required. If a fixed * address is not required, the kernel will select an address in the proper * range. * Other architectures, such as ppc64, i386 or x86_64 are not so constrained. */#include<stdlib.h>#include<stdio.h>#include<unistd.h>#include<sys/mman.h>#include<fcntl.h>#define FILE_NAME "huge/hugepagefile"#define LENGTH (256UL*1024*1024)#define PROTECTION (PROT_READ | PROT_WRITE)/* Only ia64 requires this */#ifdef __ia64__#define ADDR (void *)(0x8000000000000000UL)#define FLAGS (MAP_SHARED | MAP_FIXED)#else#define ADDR (void *)(0x0UL)#define FLAGS (MAP_SHARED)#endifstaticvoidcheck_bytes(char*addr){printf("First hex is %x\n",*((unsignedint*)addr));}staticvoidwrite_bytes(char*addr){unsignedlongi;for(i=0;i<LENGTH;i++)*(addr+i)=(char)i;}staticintread_bytes(char*addr){unsignedlongi;check_bytes(addr);for(i=0;i<LENGTH;i++)if(*(addr+i)!=(char)i){printf("Mismatch at %lu\n",i);return1;}return0;}intmain(void){void*addr;intfd,ret;fd=open(FILE_NAME,O_CREAT|O_RDWR,0755);if(fd<0){perror("Open failed");exit(1);}addr=mmap(ADDR,LENGTH,PROTECTION,FLAGS,fd,0);if(addr==MAP_FAILED){perror("mmap");unlink(FILE_NAME);exit(1);}printf("Returned address is %p\n",addr);check_bytes(addr);write_bytes(addr);ret=read_bytes(addr);munmap(addr,LENGTH);close(fd);unlink(FILE_NAME);returnret;}